Electric fuse



I. H. P. HINDs Oct. 20, 1931.

ELECTRIC FUSE Filed Dec.

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Patented 20, 19431 uNiTED STATES PATENT OFFICE" may .1. nnms, orrrr'rsrmm, MASSACHUSETTS, AssIGNoa To enermax. mcl' T RIC, A OOBPORLTIONOF NEW YORK ELECTRIC FUSE application mea 'recenser 1s, 192e. sei-:a1no. 415,011.

The present invention relates to protective devices for electricalcircuits and more especially to expulsion fuses lwhich comprise atubular housi or barrel closed at one end and open at e other withterminal contacts at both ends .to which a fusible element within thebarrelis attached.

Among the objects of my invention are the provision of an jimprovedexpulsion fuse l which shall operate with certainty when and only whenan excess current condition exlsts on the circuit rotected thereby; theprovision of an expugion fuse which shall function eiectively oncircuits of high otential and small current ratings and ein ying-suchsubstantial structure that it may be refused b the inelrpert withouterror or injury to tli'e parts. t Y f One embodiment of the invention isshown zo in the accompanyin drawin in whichlFig. -1- islan elevation. oa comp ete fuse with a part lbroken away; Fig. 2 is a vertical sectionthereof; Figs. 3 and 4 are enlar d fr.

. mentary views of the upper end of t e fusib e element and litsterminal, and Fig. 5 1s a vertical section'of a primary cut-out box at areduced scale with my fuse mounted there' The special 'uses for Awhichmy fuse is'del signed are in railway signal systems, farm systems,whereb small currents for farm use are taken from high potential werlines and other systems emplo y On account of the hig voltages and smallam of the circmts to be protected, the

cross section andin consequence they are fragile and easily-dented orotherwise l1n- ]'ured in han so that the rating may be seriously affecteMoreover, on account 0f their installation out-of-doorsyoxidation by theelements ofl the fusible element may in the i course of a shorttime soimpair the carrying .capacity of the fusible element that it disruptsunder -the ordinary rating of thecircuit and it has frequently occurredthat fusible elements of unsafely large capacity have been installed. 'iThe main arts or sections of my fusible element of tin or alloy wire smatransformers.

rages fusible elements are nrily of very small 1 of copper strip or wirepreferably plated` vwith tin or nickel. To provide mechanical strength,the first two sections of the fusible element are mounted upon anasbestos cord v 4 which is connected by crimping at its up-I per end tothe terminal disk 6, as shown n rig. 3, while its lower end is securedto the copper wire section 3 by tightly wrappingthe latter thereaboutand soldering. ln or-4 der to take the mechanical strain off' of thefuse, and keep the long double second section 2 from contacting with theinner wall 'of the enclosing barrel, it is preferably wrapped severaltimes about a strong, non-.

Wrapping, the wire is longer than the cord so that the cord takes allmechanical strains The upperl section 1, in which initial fusion takesplace, extends lfrom the upper end of the doubled "second section andisprovided at its upper end with a flexible coil or spiral conducting,non-carbonizing support suclras.'` the asbestosv cord 4 and at its upperendisfm tied about the cord. Owing -to the spiral which might be imposedon the fuse link.

5 and soldered to the terminal disk 6. This i spiral 5 permits asubstantial amount of tilting and bending at the point ofl juncture tion3 being of `copperwe1l platedand of substantially ater size than thewires of the other sections is welladapted to resist deterioration innormal service.

c The terminal disks is preferably made ff 'copper annealed to a' deadsoft temper with a crown flange 7 on itslower surface adapted to becrimped upon the end of the asbestos cord 4. y y

The housing or barrel of my fuse consists of a ,tube 8 of ndurated fibreor other stout lwith the disk such as is incident to handling insulationmaterial with contact terminals 9 and 10 attached to its opposite ends.

rlhe upper contact terminal 9 has a counter bore at its lower end inwhich the end of the tube 8 is rigidly secured by indent'ing the metalof the terminal into the sides of the tube as shown at 11. The terminal9 eX- tends a considerable distance above the end. of the tube and itsbore constitutes an extension of the bore of the insulating tube 7. Theexternal lower half of the terminal is rectangular to provide contactsurfaces 12 and the upper half is made cylindrical and threaded nearitsjuncture with the rectangular part. An internally threaded thimble 13having a hand-hold exterior surface is adapted to be screwed down uponthe thread of the terminal so that after the fusible element has beeninstalled in the barrel with. the terminal disk 6' resting upon theendof the terminal contact 9, the turning home of the thimble serves toclamp the soft copper disk 6 in intimate contact therewith to insuregood electrical connection and eifectually seal the joint against escapeof metallic gases to the threads upon blowing of the fuse.

The lower terminalcontact 10 is bored out so as to allow the insulatingtube 8 to extend entirely through and project a distance below it, asindicated in Figs. 1, 2 and 5, where the. two parts are secured togetherby indentations 14A. The lower end of the terminal contact 10 isyprovided with a conical surface 15 roughened or knurled and againstwhich the outer end of the third or copper wire section of the fusibleelement is clamped by a nut 16 engaging threads 17 above surface 15. Theupper end of the terminal 1() is made square to provide contact surfaces18. The object of roughening the conical surface 15 is to insure thatthe end of the copper wire of section 3 will .not be carried around withthe nut 16 and the fusible element twisted or otherwise injured.

The cut-out box, as shown in Fig. 5, is a standard article of commerceand need not be described in detail. lt has a stationary part 19 inwhich are secured line terminal contacts 2O and 21 for the reception ofthe fuse terminals 9 and 10. A door 21 is hinged to the front of thestationary part 19 and the two parts serveto protect the fuse and itsconnections, while the lower end of the fuse tube 8 projects through thebottom wall 22 so that upon blowing ofthe fuse the gases and theunconsumed parts of the fusible element will be expelled into the openair.

When the fuse operates on a gradual overload only the single Wiresection 1 will be volatilized as a rule. vIn case the overload 1srelatively heavy, more or less of the double wire section 2 will also bevolatilized. Upon blowingof the fuse, anyunconsumed metal part thereofand the cord support are ejected from the open end of the tube 8 butleft hangt-he conical ling from the lower terminal and thereafter serveas an indicator of the blown condition of the fuse.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,-

1. A fusible element comprising a short section of single and a longsection of double wire of soft metal, a cord of insulating materialreinforcing said sections of soft metal wire, and relatively hard metalterminals joined to opposite ends of said cord and said soft metal wire.y

2. A fusible element comprising an end terminal, a cord of insulatingmaterial fastened at one end to said terminal, and a fuse wire supportedby said cord and joined to said terminal and provided adjacent the jointwith a freely yieldable bent portion.

3. A fusible element comprising an end terminal disk with a crown flangeprojecting from one side, a cord of insulating material having one endconnected to said terminal disk by crimping said flange thereon, and afuse wire supported by said cord and joined to said terminal disk andprovided adjacent said joint with a flat spiral alongside said crimpedflange.

4. A fusible element comprising a disk terminal, a cord of insulatingmaterial clamped to one side of said terminal, a thin fuse wire of softmetal supported'by said cord and having a flexible coil adjacent the endjoined to said disk terminal, and a terminal of relatively thick andhard metal secured to theopposite ends of said cord and said soft metalwire.

5. A fuse barrel comprising a tube of insulating material, a terminalcontact mounted about one end of said tube and provided externally witha roughened conical surface and a screw thread adjacent said conicalYsurface5 and a. clamping nutA adapted to fsurround saidconical surfaceand engage sa1d screw thread.

6. A fuse barrel comprising a tube of 1 11- sulating material, a fusibleelement therein,

a contact terminal provided with means for engaging an end of saidfusible element and hermetically closing one end of said tube, a secondcontact terminal secured adjacent the other end of said tube andprovided with a knurled conical surface for'positive clamping engagementwith the other end of said fusible element, and a clamping nut threadedupon said second terminal and adapted t0 force the fusible element intointimate contact with said knurled conical surface thereo 7. Thecombination of an insulating barrel provided with metal terminals at`its ends, one of which is open, a fusible element .disposed within saidbarrel and comprising an end disk of annealed copper for closing theother endof said barrel, said Vdisk being in .electrical connection withtheterminal at the esA closed end, a of fusible metal and areinforcement cord therefor each having one end attached to said enddisk, and a copperl strip joined to the opposite ends of said fusiblelink and said cord within said barrel and extending. out the open endthereof and attached to the metal terminal adjacent thereto.

8. The combination of an insulating barrel provided at its ends withclamping metal terminals, one of rwhich is open and the other normallyclosed, a fusible element disposed within said `barrel and comprising anend disk in electrical connection with said closed terminal and providedon its inner side with a crown iiange, a cord of asbestos having one endfastened to said end disk by crimping said flange thereupon a link ofsoft metal fastened to said cord and having one end iiexibly joined tosaid end disk, and a strip of copper protected against oxidation joinedto the said cord and said link within the barrel and extending out theopen end thereof, bent back- Wardly and clamped to said open terminal.

9. The combination of an insulating barrel provided at its ends withmetallic clamping terminals, one adapted to close the upper end of saidbarrel and the other surrounding said barrel adjacent the lower open endthereof, a fusible element comprising a member to be clamped to saidupper terminal, an insulatf ing cord and a soft metal link each havingone end attached to said disk, said link being made double except for ashort section at its upper end and fastened to said cord, and a hardmetal strip joined'to the opposite ends of said cord and said link andextending out the open end. of said barrel and clamped to the lowerterminal thereof.

In witness whereof, I have hereunto set my hand this 16th day of Dec.,1929.

HENRY P. HINDS.

